Effects of different substrates on the sprint performance of lizards.
ABSTRACT The variation in substrate structure is one of the most important determinants of the locomotor abilities of lizards. Lizards are found across a range of habitats, from large rocks to loose sand, each of them with conflicting mechanical demands on locomotion. We examined the relationships among sprint speed, morphology and different types of substrate surfaces in species of lizards that exploit different structural habitats (arboreal, saxicolous, terrestrial and arenicolous) in a phylogenetic context. Our main goals were to assess which processes drive variability in morphology (i.e. phylogeny or adaptation to habitat) in order to understand how substrate structure affects sprint speed in species occupying different habitats and to determine the relationship between morphology and performance. Liolaemini lizards show that most morphological traits are constrained by phylogeny, particularly toe 3, the femur and foot. All ecological groups showed significant differences on rocky surfaces. Surprisingly, no ecological group performed better on the surface resembling its own habitat. Moreover, all groups exhibited significant differences in sprint speed among the three different types of experimental substrates and showed the best performance on sand, with the exception of the arboreal group. Despite the fact that species use different types of habitats, the highly conservative morphology of Liolaemini species and the similar levels of performance on different types of substrates suggest that they confer to the 'jack of all trades and master of none' principle.
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ABSTRACT: Trade-offs are thought to be important in constraining evolutionary divergence, as they may limit phenotypic diversification. Limbless animals that burrow head-first have been suggested to be evolutionarily constrained in the development of a large head size and sexual head shape dimorphism because of potential trade-offs associated with burrowing. Here we use an acontiine skink (Acontias percivali) to test for the existence of trade-offs between traits thought to be important in burrowing (speed and force). As head size dimorphism has been shown to be limited in acontiine lizards, thus suggesting constraints on head size and shape, we additionally explore the potential for trade-offs between burrowing and biting. Our data show that A. percivali uses a burrowing style different from those previously described for caecilians and amphisbaenians, which relies on the use of extensive lateral and dorsoventral head movements. Our data also show that animals use their entire bodies to generate force, as peak force was determined by total length only. Additionally, both bite force and the time needed to burrow into the substrate were principally determined by relative head width, suggesting a trade-off between biting and burrow speed. Performance data were indeed suggestive of a correlation between bite force and the time needed to burrow, but additional data are needed to confirm this pattern. In summary, our data suggests that trade-offs may exist, and may have been of crucial importance in shaping the evolution of head shape in A. percivali, and burrowing lizards more generally. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 91–99.Biological Journal of the Linnean Society 12/2010; 102(1):91 - 99. · 2.41 Impact Factor
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ABSTRACT: Tropidurid lizards have colonized a variety of Brazilian open environments without remarkable morphological variation, despite ecological and structural differences among habitats used. This study focuses on two Tropidurus sister-species that, despite systematic proximity and similar morphology, exhibit great ecological divergence and a third ecologically generalist congeneric species providing an outgroup comparison. We quantified jumping capacity and sprint speed of each species on sand and rock to test whether ecological divergence was also accompanied by differences in locomotor performance. Relevant physiological traits possibly associated with locomotor performance - metabolic scopes and fiber type composition, power output and activity of the enzymes citrate synthase, pyruvate kinase and lactate dehydrogenase of the iliofibularis muscle - were also compared among the three Tropidurus species. We found that the two sister-species exhibited remarkable differences in jumping performance, while Tropidurus oreadicus, the more distantly related species, exhibited intermediate values. Tropidurus psamonastes, a species endemic to sand dunes, exhibited high absolute sprint speeds on sand, jumped rarely and possessed a high proportion of glycolytic fibers and low activity of citrate synthase. The sister-species Tropidurus itambere, endemic to rocky outcrops, performed a large number of jumps and achieved lower absolute sprint speed than T. psamonastes. This study provides evidence of rapid divergence of locomotor parameters between sister-species that use different substrates, which is only partially explained by variation in physiological parameters of the iliofibularis muscle.Journal of Experimental Biology 04/2004; 207(Pt 7):1183-92. · 3.24 Impact Factor
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ABSTRACT: We examined clinging ability, subdigital pad area and body mass in 14 pad-bearing lizard species from three families to test three predictions: (1) clinging ability and pad area should be tightly correlated among species; (2) pad area and clinging ability should scale similarly to body mass among 14 species; and (3) functional similarity in clinging capabilities should exist among species despite differences in body mass. Our results confirm two predictions; clinging ability is tightly correlated with pad area, even when the effects of body size are removed, and the lizards examined are approximately functionally similar in their clinging capabilities. Nevertheless, despite the tight correlation between pad area and clinging ability, pad area scales with body mass by a lower slope than clinging ability. Overall, these results indicate that although pad area is a strong determinant of clinging ability, other factors enable these lizards to maintain functional similarity.Biological Journal of The Linnean Society - BIOL J LINN SOC. 01/1996; 59(1).